CLINICAL REPORT ADULT BRAIN BrainMagnetic Susceptibility Changes in Patients with Natalizumab-Associated ProgressiveMultifocal Leukoencephalopathy

SUMMARY: We investigated the brain magnetic susceptibility changes induced by natalizumab-associated progressive multifocal leukoencephalopathy. We retrospectively included 12 patients with natalizumab–progressive multifocal leukoencephalopathy, 5 with progressivemultifocal leukoencephalopathy fromother causes, and 55 patients withMSwithout progressivemultifocal leukoencephalopathy for comparison. MR imaging examinations included T2* or SWI sequences in patients with progressive multifocal leukoencephalopathy (86 examinations) and SWI in all patients with MS without progressive multifocal leukoencephalopathy. Signal abnormalities on T2* and SWI were defined as low signal intensity within the cortex and/or U-fibers and the basal ganglia. We observed T2* or SWI signal abnormalities at the chronic stage in all patients with progressive multifocal leukoencephalopathy, whereas no area of low SWI signal intensity was detected in patients without progressive multifocal leukoencephalopathy. Among the 8 patients with asymptomatic natalizumab– progressive multifocal leukoencephalopathy, susceptibility changes were observed in 6 (75%). The basal ganglia adjacent to progressive multifocal leukoencephalopathy lesions systematically appeared hypointense by using T2* and/or SWI. Brain magnetic susceptibility changes may be explained by the increased iron deposition and constitute a useful tool for the diagnosis of progressive multifocal leukoencephalopathy. ABBREVIATIONS: NTZ natalizumab; PML progressive multifocal leukoencephalopathy Natalizumab (NTZ), an effective treatment in patients with relapsing-remitting multiple sclerosis, is associated with a risk of progressive multifocal leukoencephalopathy (PML). Early diagnosis of NTZ-associated PML (NTZ-PML) may improve the functional outcome. However, the diagnosis of asymptomatic NTZ-PML remains difficult due to the coexistence of MS lesions and the different imaging patterns of NTZ-PML lesions. MR imaging is crucial for the recognition of NTZ-PML. The known imaging findings for asymptomatic NTZ-PML include the following: a subcortical location involving U-fibers, a sharp lesional border toward the gray matter contrasting with an ill-defined border toward the white matter, and increased signal intensity on T2-weighted and diffusion-weighted images. Postcontrast enhancement and T2WI hyperintense punctate lesions have also been reported in patients with NTZ-PML. To our knowledge, there are no data available on the susceptibility changes, evaluated by gradient-echo T2* or susceptibilityweighted images, in a cohort of consecutive patients with NTZPML. Our purpose was to investigate the brain magnetic susceptibility changes, detected on T2* or SWI, in a cohort of consecutive patients with NTZ-PML.